A product owner is a key role in agile project management, primarily responsible for defining the vision of a product and ensuring that the development team delivers value to the customers. They prioritize the product backlog, which is a list of tasks and features that need to be completed, and communicate with stakeholders to gather requirements and feedback. In collaboration with the scrum master and the development team, the product owner makes decisions about what to build next and clarifies any questions regarding the product features. Their goal is to maximize the return on investment (ROI) by aligning the product development with customer needs and business objectives.